The goal of this project is to assist the NIDR initiative to characterize the mucosal immune response to HIV, the causative agent of AIDS. Under contract No. N01-DE-42600 with the University of Minnesota, studies have focused on several aspects of the mucosal immune response to HIV infection and its involvement in protection or susceptibility to HIV infection. It is planned to extend these studies on the role of specific and innate host factors which contribute to resistance or susceptibility to vertical retroviral transmission. The objectives of the extended project are to develop and employ the methods and assays for selected immunological and viral characteristics in oral and interestinal fluids and tissues in the U.S., and breast milk and serum in a cohort of HIV-infected, pregnant women and their infants in Africa. The latter are part of a study group currently participating in a Phase III study in Bobo Dioulasso, Burkina Faso, Africa. The infectivity of breast milk over time after delivery will be characterized and the results correlated with clinical, virologic and immunologic factors in HIV-infected mothers.